Multi-layered printed wiring board

ABSTRACT

A multi-layered printed wiring board capable of securing required wiring density even with a decreased number of wiring layers and reducing radiation noises. The multi-layered printed wiring board has at least three wiring layers each at least having at least one power supply line or a ground line, and another kind of line, said wiring layers each having an outer edge. A ground line is formed at the outer edge of at least one of the wiring layers. A basic power supply line is formed inside the ground line. At least one power supply line extends from the basic power supply line. A plurality of electronic parts are mounted on at least one of the wiring layers. The at least one power supply line is wired to mounting positions of the electronic parts via at least one of the wiring layers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a multi-layered printed wiring board having aplurality of wiring layers, and more particularly to a multi-layeredprinted wiring board that is suitably applied to achieve high-densitywiring.

2. Description of the Related Art

In recent years, with the advancement of functions of digital equipment,an increasing number of printed wiring boards installed on digitalequipment have been equipped with a great number of multi-pin packagedsemiconductor devices such as the BGA (Ball Grid Array). Such multi-pinpackaged semiconductor devices include integrated circuits having 500pins or more. The wiring density of such printed wiring boards has beenraised with the increase in the number of pins. This necessitatesincreasing the number of wiring layers of printed wiring boards, and ifa multi-layered printed wiring board having four layers cannot house allrequired lines, a multi-layered printed wiring board having six layersor a multi-layered printed wiring board having eight layers is used.

Japanese Laid-open Patent Publication (Kokai) No. 10-270862 discloses anexample of conventional multi-layered printed wiring boards (first priorart). According to this prior art, a plurality of circuit elements aremounted on the multi-layered printed wiring board, and a ground layer, asignal layer, and a power supply layer providing the circuit elementswith power supply voltages are laminated one upon another via respectiveinsulating materials. The respective circuit elements are classifiedinto a plurality of groups according to the operating speed, and regionsfor mounting the circuit elements on the multi-layered printed wiringboard are determined according to the groups. In the power supply layer,power supply lines are formed according to the groups, and a power line,which separates the power supply lines from one another against highfrequencies, connects between the power supply lines belonging todifferent groups. In this connection, the multi-layered printed wiringboard must be provided with a ground-only layer comprised only of groundlines and a power supply-only layer comprised only of power supply linesin order to reduce radiation noises.

Further, Japanese Laid-open Patent Publication (Kokai) No. 7-321429discloses an example of conventional double-layered printed wiringboards (second prior art). In the printed wiring board according to thisprior art, ground lines and power supply lines are provided in the formof a grid in each of the wiring layers such that they extend in paralleland are alternately arranged, and the wiring layers are arranged suchthat the lines of a first wiring layer and those of a second layervertically intersect each other, and the ground lines and the powersupply lines in the respective wiring layers are connected together viathrough holes. This arrangement enables a solid ground and reducesradiation noises.

The above described prior arts, however, have the following problems:

The increase in the number of layers as in the first prior art toaccommodate all required lines easily realizes high-density wiring, butincreases the time and cost required for manufacturing the printedwiring board.

Providing ground lines and power supply lines in the form of a grid oneach of the wiring layers as in the second prior art reduces radiationnoises, but imposes a lot of restrictions on a space for wiring signallines and makes it difficult to achieve high-density wiring.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide amulti-layered printed wiring board that is capable of securing requiredwiring density even with a decreased number of wiring layers andreducing radiation noises.

To attain the above object, a first aspect of the present inventionprovides a multi-layered printed wiring board having at least threewiring layers each at least having at least one power supply line or aground line, and another kind of line, said wiring layers each having anouter edge, comprising the ground line formed at the outer edge of atleast one of the wiring layers, a basic power supply line formed insidethe ground line, the at least one power supply line extending from thebasic power supply line, a plurality of electronic parts mounted on atleast one of the wiring layers, and wherein the at least one powersupply line is wired to mounting positions of the electronic parts viaat least one of the wiring layers.

Preferably, the ground line and the basic power supply line are eachshaped substantially in a form of annulus and arranged adjacent to eachother.

Preferably, the multi-layered printed wiring board according to thefirst aspect comprises a signal line provided in each of the wiringlayers, the signal line connecting between ones of the electrical partsmounted on one of the wiring layers or connecting between ones of theelectrical parts mounted on respective different ones of the wiringlayers via at least one of the wiring layers, and wherein the powersupply line and the signal line are formed inside the basic power supplyline.

To attain the above object, a second aspect of the present inventionprovides a multi-layered printed wiring board having at least threewiring layers each at least having at least one power supply line or aground line, and another kind of line, said wiring layers each having anouter edge, comprising the ground line formed at the outer edge of atleast one of the wiring layers, a plurality of electronic parts mountedon at least one of the wiring layers, the at least one power supply lineprovided in a predetermined one of the wiring layers at a locationinside the ground line, the at least one power supply line being wiredto mounting positions of the electronic parts via at least one other oneof the wiring layers, a signal line provided in each of the wiringlayers, the signal line connecting between ones of the electrical partsmounted on one of the wiring layers or connecting between ones of theelectrical parts mounted on respective different ones of the wiringlayers via at least one of the wiring layers, and a ground patternformed over a region other than the power supply line and the signalline and connected to the ground line.

Preferably, in the multi-layered printed wiring board according to thesecond aspect, the ground line and ground pattern are formed such thatthe ground line and ground pattern substantially entirely cover themulti-layered printed wiring board when the ground line and groundpattern are projected on one projection plane.

Also preferably, the multi-layered printed wiring board according to thesecond aspect comprises a basic power supply line formed at the outeredge of at least one of the wiring layers at a location adjacent to andinside the ground line, wherein the power supply line is formed insidethe basic power supply line and extends from the basic power supply linevia at least one of the wiring layers such that the power supply line iswired to mounting positions of the electrical parts, and the signal lineis formed inside the basic power supply line, the signal line connectingbetween ones of the electrical parts mounted on one of the wiring layersor connecting between ones of the electrical parts mounted on respectivedifferent ones of the wiring layers via at least one of the wiringlayers.

Preferably, in the multi-layered printed wiring board according to thesecond aspect, the ground line and the basic power supply line are eachshaped substantially in a form of annulus and arranged adjacent to eachother.

Preferably, in the multi-layered printed wiring board according to thesecond aspect, the power supply line and the power supply line arearranged so as not to overlap the power supply line and the signal linein at least one other one of the wiring layers which is adjacent to theat least one of the wiring layers in which the power supply line isformed, when the power supply lines and the signal lines are projectedon one projection plane.

To attain the above object, a third aspect of the present inventionprovides a multi-layered printed wiring board having at least threewiring layers each at least having at least one power supply line or aground line, and another kind of line, said wiring layers each having anouter edge, the multi-layered printed wiring board comprising a firstwiring layer constituting one of the wiring layers, and having groundline formed at the outer edge of the first wiring layer, a first basicpower supply line formed adjacent to and inside the ground line, and afirst power supply line extending from the first basic power supplyline, a second wiring layer constituting one of the wiring layers, andhaving a ground pattern formed at the outer edge of the second wiringlayer, a second basic power supply line for supplying a differentvoltage from a voltage supplied by the first basic power supply line,the second basic power supply line being formed at a position where thefirst basic power supply line is projected when the second basic powersupply line and the first basic power supply line are projected on oneprojection plane, and a second power supply line extending from thesecond basic power supply line, and a plurality of electronic partsmounted on at least one of the wiring layers, wherein the first andsecond power supply lines extending from the first and second basicpower supply lines, respectively are wired to mounting positions of theelectronic parts via at least one of the wiring layers.

Preferably, in the multi-layered printed wiring board according to thethird aspect, the ground line and ground pattern and the first andsecond basic power supply lines are each shaped substantially in a formof annulus.

Also preferably, the multi-layered printed wiring board according to thethird aspect comprises a signal line provided in each of the wiringlayers, the signal line connecting between ones of the electrical partsmounted on one of the wiring layers or connecting between ones of theelectrical parts mounted on respective different ones of the wiringlayers via at least one of the wiring layers, and a ground patternformed over a region other than the first and second power supply linesand the signal line and connected to the ground line and ground pattern,and wherein the first and second power supply lines and the signal lineare formed inside the first and second basic power supply lines.

To attain the above object, a fourth aspect of the present inventionprovides a multi-layered printed wiring board having at least threewiring layers each at least having at least one power supply line or aground line, and another kind of line, said wiring layers each having anouter edge, comprising the ground line formed at the outer edge of atleast one of the wiring layers, a first basic power supply line formedadjacent to and inside the ground line, a second basic power supply lineformed adjacent to and inside the ground line to supply a differentvoltage from a voltage supplied by the first basic power supply line, atleast two power supply lines extending from respective ones of the firstand second basic power supply lines, a plurality of electronic partsmounted on at least one of the wiring layers, and wherein the powersupply lines are wired to mounting positions of the electronic parts viaat least one of the wiring layers.

Preferably, in the multi-layered printed wiring board according to thefourth aspect, the ground line and the first and second basic powersupply lines are shaped substantially in a form of annulus.

Also preferably, the multi-layered printed wiring board according to thefourth aspect comprises a signal line provided in each of the wiringlayers, the signal line connecting between ones of the electrical partsmounted on one of the wiring layers or connecting between ones of theelectrical parts mounted on respective different ones of the wiringlayers via at least one of the wiring layers, and a ground patternformed over a region other than the power supply lines and the signalline and connected to the ground line, and wherein the power supplylines and the signal line are formed inside the second basic powersupply line.

To attain the above object, a fifth aspect of the present inventionprovides a multi-layered printed wiring board having at least threewiring layers each at least having at least one power supply line or aground line, and another kind of line, said wiring layers each having anouter edge, comprising the ground line formed at the outer edge of eachof the wiring layers, a basic power supply line formed adjacent to andinside the ground line in each of the wiring layers, a plurality ofelectronic parts mounted on at least one of the wiring layers, the atleast one power supply line provided in at least one of the wiringlayers at a location inside the basic power supply line, the at leastone power supply line extending from the basic power supply line via atleast one other one of the wiring layers and wired to mounting positionsof the electronic parts, a signal line provided in each of the wiringlayers, the signal line connecting between ones of the electrical partsmounted on one of the wiring layers or connecting between ones of theelectrical parts mounted on respective different ones of the wiringlayers via at least one of the wiring layers, and a ground patternformed over a region other than the power supply line and the signalline at a location inside the basic power supply line in at least one ofthe wiring layers, and wherein the ground line in at least one of thewiring layers has a width greater than the ground line in the otherwiring layers and connected to the ground pattern via at least onethrough hole.

In the multi-layered printed wiring board according to the presentinvention, the ground line is formed at the outer edge of at least oneof the wiring layers and the basic power supply line is formed insidethe ground line, and the power supply line and the signal line extendfrom the basic power supply line to mounting positions of the electronicparts via at least one of the wiring layers. This enables higher-densitywiring without lowering the wiring density compared with a multi-layeredprinted wiring board having a ground-only layer and a power supply-onlylayer.

Further, since the power supply line and the signal line are wiredinside the annular basic power supply line in the wiring layer or layersin which they are provided, the degree of freedom in wiring signal linescan be increased.

Further, since the basic power supply line and the ground line areannular in shape and wired adjacent to each other, the capacitiveconnection between the basic power supply line and the ground line isimproved to reduce radiation noises.

Further, in the wiring layer or layers in which the power supply lineand the signal line are provided, the ground patterns are formed over aregion other than the signal line and the power supply line, and areconnected together via through holes. This forms stable grounding andreduces radiation noises.

Further, the ground lines and ground patterns in the respectivedifferent wiring layers cover the entire surface of the multi-layeredprinted wiring board when they are projected on the same projectionplane. This forms more stable grounding and reduces radiation noises.

Further, since the signal line and the power supply line are wired atsuch positions that they do not overlap the signal lines and the powersupply lines in adjacent wiring layers when they are projected on thesame projection plane. This reduces the effect of cross talk.

Further, since the ground lines in the respective different wiringlayers are connected together via through holes, radiation noises can besatisfactorily reduced without providing a ground-only layer.

Therefore, the multi-layered printed wiring board according to thepresent invention is capable of reducing radiation noises withoutlowering the wiring density even if the number of wiring layers isdecreased.

The above and other objects of the invention will become more apparentfrom the following detailed description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D are schematic diagrams showing the construction of amulti-layered printed wiring board according to a first embodiment ofthe present invention;

FIG. 2 is a schematic diagram showing the construction of all layers ofthe printed wiring board according to the first embodiment asfluoroscopically viewed from above;

FIGS. 3A-3D are schematic diagrams showing only ground lines on theprinted wiring board according to the first embodiment;

FIG. 4 is a schematic diagram showing only ground lines in each of thelayers of the printed wiring board according to the first embodiment asfluoroscopically viewed from above;

FIGS. 5A-5D are schematic diagrams showing the construction of amulti-layered printed wiring board according to a second embodiment ofthe present invention;

FIGS. 6A-6D are schematic diagrams showing the construction of amulti-layered printed wiring board according to a third embodiment ofthe present invention;

FIG. 7 is a schematic diagram showing the construction of all layers ofthe printed wiring board according to the third embodiment as viewedfrom above with layer substrates omitted;

FIGS. 8A-8D are schematic diagrams showing the construction of amulti-layered printed wiring board according to a fourth embodiment ofthe present invention; and

FIG. 9 is a schematic sectional view showing a section of themulti-layered printed wiring board according to the fourth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in detail with reference tothe accompanying drawings showing preferred embodiments thereof.

(First Embodiment)

FIGS. 1A-1D are schematic diagrams showing the construction of amulti-layered printed wiring board according to a first embodiment ofthe present invention. FIG. 2 is a schematic diagram showing theconstruction of all layers of the multi-layered printed wiring boardaccording to the first embodiment as viewed from above, and is intendedto provide a supplemental explanation of the connection and positionalrelationship between signal lines.

The multi-layered printed wiring board according to the first embodimentis comprised of a first wiring layer 1, a second wiring layer 2, a thirdwiring layer 3, and a fourth wiring layer 4, which are shown in FIGS.1A-1D, respectively. These wiring layers are laminated one upon anotherin the order mentioned. Each of the wiring layers are comprised of asubstrate, and various wiring lines provided on a surface of thesubstrate. This basic construction applies to other embodiments,described later.

As shown in FIG. 1A, electronic parts 7 a, 7 b, 7 c are mounted on thefirst wiring layer 1, and signal lines 6 a, 6 b and a ground pattern 8 aare provided in the first wiring layer 1. The signal line 6 a connectsbetween the electronic part 7 a in the first wiring layer 1 and anelectronic part 7 e in the fourth layer 4, appearing in FIG. 1D, viathrough holes, not illustrated. The signal line 6 b connects between theelectronic part 7 b and the electronic part 7 c. In the first wiringlayer 1, the ground pattern 8 a is formed over a substantially entirearea of a major surface of the substrate at regions other than thesignal lines such that the minimum required clearances in terms ofmanufacture are provided between the ground pattern 8 a and a powersupply line and the signal lines.

As shown in FIG. 1B, an annular ground line 8 is provided in the secondwiring layer 2, and an annular basic power supply line 5 is providedinside the ground line 8. The annular ground line 8 is formed at aregion along the outer edge of the substrate, and inside the ground line8 the annular basic power supply line 5 is formed along the ground linesuch that the minimum required clearances in terms of manufacture areprovided between the two lines 8 and 5. Signal lines 6 c, 6 d and aground pattern 8 b are provided inside the basic power supply line 5.The signal line 6 c connects between the electronic part 7 a in thefirst layer 1 and an electronic part 7 d in the fourth layer 4,appearing in FIG. 1D, via through holes, not illustrated. The signalline 6 d connects between the electronic part 7 c in the first wiringlayer 1 and an electronic part 7 e in the fourth wiring layer 4,appearing in FIG. 1D, via through holes, not illustrated. A power supplyline 5 a is provided inside the basic power supply line 5, whichconnects between the basic power supply line 5 and the electronic part 7b in the first wiring layer 1 via through holes, not illustrated. Insidethe basic power supply line 5 in the second wiring layer 2, the groundpattern 8 b is formed over a region other than the power supply line andthe signal lines such that the minimum required clearances in terms ofmanufacture are provided between the ground pattern 8 b and the powersupply line and the signal lines.

As shown in FIG. 1C, signal lines 6 e, 6 f, power supply lines 5 b, 5 c,5 d, 5 e, and a ground line 6 c are provided in the third wiring layer3. The signal line 6 e connects between the electronic part 7 b in thefirst wiring layer 1 and the electronic part 7 d in the fourth layer 4,appearing in FIG. 1D, via through holes, not illustrated. The signalline 6 f connects between the electronic part 7 c in the first wiringlayer 1 and the electronic part 7 e in the fourth wiring layer 4,appearing in FIG. 1D, via through holes, not illustrated. The powersupply line 5 b connects between the electronic part 7 a in the firstwiring layer 1 and the basic power supply line 5 in the second wiringlayer 2 via through holes, not illustrated. The power supply line 5 cconnects between the basic power supply line 5 in the second wiringlayer 2 and the electronic part 7 d in the fourth wiring layer 4,appearing in FIG. 1D, via through holes, not illustrated. The powersupply line 5 d connects between the basic power supply line 5 in thesecond wiring layer 2 and the electronic part 7 e in the fourth wiringlayer 4 via through holes, not illustrated. The power supply line 5 econnects between the basic power supply line 5 in the second wiringlayer 2 and the electronic part 7 c in the first wiring layer 1 viathrough holes, not illustrated. In the third wiring layer 3, the groundpattern 8 c is formed over a region other than the power supply linesand the signal lines such that the minimum required clearances in termsof manufacture are provided between the ground pattern 8 c and the powersupply lines and the signal lines.

As shown in FIG. 1D, the electronic parts 7 d, 7 e are mounted on thefourth wiring layer 4. Signal lines 6 g, 6 h, 6 i, a power supply line 5f and a ground pattern 8 d are also provided in the fourth wiring layer4. The signal line 6 g connects between the electronic part 7 a and theelectronic part 7 b in the first wiring layer 1 via through holes, notillustrated. The signal line 6 h connects between the electronic part 7c in the first wiring layer 1 and the electronic part 7 d in the fourthwiring layer 4 via through holes, not illustrated. The signal line 6 iconnects between the electronic part 7 e in the fourth wiring layer 4and the electronic part 7 b in the first wiring layer via through holes,not illustrated. In the fourth wiring layer 4, the ground pattern 8 d isformed over a region other than the power supply lines and the signallines such that the minimum required clearances in terms of manufactureare provided between the ground pattern 8 d and the power supply linesand the signal lines.

It should be noted that the ground line 8 and gournd patterns 8 a to 8 din the respective wiring layers are connected together via throughholes, not illustrated. Therefore, the annular ground line 8 in thesecond wiring layer 2 is designed to have at least a width that allowsformation of the through holes. Likewise, the annular basic power supplyline 5 is designed to have a width that allows formation of throughholes. As is clear from FIG. 2, all of the signal lines 6 a to 6 i inthe respective wiring layers are provided inside the power supply line 5in the second wiring layer 2. The ground patterns 8 a to 8 d in therespective wiring layers are omitted from FIG. 2 to make the drawingsmore understandable.

According to the first embodiment, the power supply wiring extends fromthe basic power supply line 5 in the second wiring layer 2 up to thethird wiring layer 3 and the fourth wiring layer 4 in addition to thesecond wiring layer 2 so that power can be supplied to the electronicparts mounted on the first wiring layer 1 and the fourth wiring layer 4.The signal wiring is extended over all of the first wiring layer 1, thesecond wiring layer 2, the third wiring layer 3, and the fourth wiringlayer 4. That is, the power supply wiring and the signal wiring can befreely wired on all the wiring layers, and this enables high-densitywiring.

It should be noted that, as shown in FIG. 2, the power supply lines 5 ato 5 f and the signal lines 6 a to 6 i are wired such that the lines onadjacent wiring layers do not overlap each other. This reduces theeffect of cross talk caused by adjacent lines to the least possiblelevel. Although the power supply line 5 b and the signal line 6 apartially overlap each other in FIG. 2, this does not matter since thepower supply line 5 b is wired in the third wiring layer 3 and thesignal line 6 a is wired in the first wiring layer 1.

Further, since the ground patterns 8 a to 8 d in the respective wiringlayers cover the regions other than the power supply lines and thesignal lines, no limitation is imposed on the route of ground currentthat is one of sources for generating radiation noises. Thus, the groundcurrent can flow (vertically and horizontally) in the vicinity of thesignal lines, and this reduces radiation noises.

FIGS. 3A-3D are schematic diagrams showing only the ground line 8 andground patterns 8 a to 8 d on the multi-layered printed wiring board inFIGS. 1A to 1D, and FIG. 4 is a diagram showing the respective wiringlayers of the multi-layered printed wiring board in FIGS. 1A to 1D asfluoroscopically viewed from above. If the ground line 8 and groundpatterns 8 a to 8 d in the respective wiring layers are projected on thesame projection plane as shown in FIG. 4, they cover the entire surfaceof the multi-layered printed wiring board. This arrangement leads toachievement of more stable grounding.

Although in the first embodiment the ground lines thus cover the entiresurface of the multi-layered printed wiring board, it goes withoutsaying that they should not necessarily cover the entire surface insofaras they cover substantially the entire surface, providing substantiallythe same effects. The ground line 8 may be provided in two or morewiring layers. Still further, although in the first embodiment theground line 8 and the basic power supply line 5 are annular in shape,this is not limitative, but they may have other shapes insofar as theyare substantially annular in shape. Further, although in the firstembodiment the multi-layered printed wiring board has four layers, thisis not limitative but insofar as they have three or more layers and haveno ground-only layer nor power supply-only layer, the object of thepresent invention can be achieved.

As described above, in the multi-layered printed wiring board accordingto the first embodiment, the ground line 8 is formed at the outer edgeof at least one wiring layer among the four wiring layers, and the basicpower supply line 5 is formed inside the ground line 8, and the powersupply lines 5 a to 5 e and the signal lines 6 a to 6 i extend from tothe mounting positions of the electronic parts via at least one of thewiring layers. This enables higher-density wiring without lowering thewiring density compared with a multi-layered printed wiring board havingsix layers including a ground-only layer and a power supply-only layer.

Further, since the power supply lines 5 a to 5 f and the signal lines 6a to 6 f in the respective wiring layers are wired inside the annularbasic power supply line 5 and the annular basic power supply line 5 isformed at the outer edge of the wiring layer, the inside-wired powersupply lines can be arranged with high efficiency and the degree offreedom in wiring the signal lines can be increased.

Further, since the basic power supply line 5 and the ground line 8 areshaped in the annular form and arranged adjacent to each other, thecapacitive connection between the basic power supply line 5 and theground line 8 is improved to reduce radiation noises.

Further, since the ground patterns 8 a to 8 d in the respective wiringlayers are formed over the regions other than the signal lines 6 a to 6i and the power supply lines 5 a to 5 f and are connected together viathe through hole, the more stable ground can be formed and radiationnoises can be reduced.

Further, the ground line 8 and ground patterns 8 a to 8 d in therespective wiring layers are formed to cover the entire surface of themulti-layered printed wiring board when they are projected on the sameprojection plane, more stable grounding can be achieved and radiationnoises can be reduced.

Further, since the signal lines 6 a to 6 i and the power supply lines 5a to 5 f in the respective wiring layers are wired such that the signallines and the power supply lines in the adjacent wiring layers do notoverlap each other, the effect of cross talk can be reduced.

Further, since the ground patterns 8 a to 8 d in the respective wiringlayers are connected to the ground line 8 in at least one wiring layervia through holes, the effect of fully suppressing radiation noises canbe provided even without a ground-only wiring layer.

As described above, the multi-layered printed wiring board according tothe first embodiment is capable of reducing radiation noises withoutlowering the wiring density even if the number of wiring layers isdecreased.

(Second Embodiment)

FIGS. 5A-5D are schematic diagrams showing the construction of amulti-layered printed wiring board according to a second embodiment ofthe present invention.

The multi-layered printed wiring board according to the secondembodiment supplies power to electronic parts 17 a, 17 b, 17 c driven ata first voltage, and electronic parts 17 a′, 17 b′ driven at a secondvoltage different from the first voltage.

The multi-layered printed wiring board according to the secondembodiment is comprised of a first wiring layer 11, a second wiringlayer 12, a third wiring layer 13, and a fourth wiring layer 14. Theelectronic parts driven at different two voltages are mounted on thefirst wiring layer 11 and the fourth wiring layer 14.

As shown in FIG. 5A, the electronic parts 17 a, 17 b, 17 c driven at thefirst voltage and the electronic parts 17 a′, 17 b′ driven at the secondvoltage are mounted on the first wiring layer 11, and signal lines 16 a,16 b and a ground pattern 18 a are provided in the first wiring layer 11in a similar arrangement to that in FIG. 1A. The signal line 16 aconnects between the electronic part 17 a and the electronic part 17 cin the fourth layer 14, appearing in FIG. 5D, via through holes, notillustrated. The signal line 16 b connects between the electronic part17 a and the electronic part 17 b′. The power supply line 15 a connectsbetween the electronic part 17 a and a first basic power supply line 15in the second wiring layer 12, appearing in FIG. 5B, via through holes,not illustrated. In the first wiring layer 11, the ground pattern 8 a isformed over a substantially entire area of a major surface of thesubstrate at regions other than the power supply line and the signallines such that the minimum required clearances in terms of manufactureare provided between the ground pattern 18 a and the power supply lineand the signal lines.

As shown in FIG. 5B, an annular ground line 18 is provided at the outeredge of the second wiring layer 12, and the first annular basic powersupply line 15 is provided inside and along the ground line 18. Signallines 16 c, 16 d and a ground pattern 18 b are provided inside the firstbasic power supply line 15. The signal line 16 c connects between theelectronic part 17 a′ in the first layer 11 and the electronic part 17 bin the fourth layer 4 via through holes, not illustrated. The signalline 16 d connects between the electronic part 17 b′ in the first wiringlayer 11 and the electronic part 17 c in the fourth wiring layer 14 viathrough holes, not illustrated. A power supply line 15 b that connectsbetween the first basic power supply line 15 and the electronic part 17a in the first wiring layer 11 via through holes, not illustrated, apower supply line 15 c that connects between the first basic powersupply line 15 and the electronic part 17 b in the fourth wiring layer14 via through holes, not illustrated, a power supply line 15 d thatconnects between the first basic power supply line 15 and the electronicpart 17 c in the fourth wiring layer 14 via through holes, notillustrated are provided inside the first basic power supply line 15.Inside the first basic power supply line 15 in the second wiring layer12, the ground pattern 18 b is formed over a region other than the powersupply line and the signal lines such that the minimum requiredclearances in terms of manufacture are provided between the groundpattern 18 b and the power supply line and the signal lines.

As shown in FIG. 5C, an annular ground line 18 e is provided in thethird wiring layer 3, and a second annular basic power supply line 15′is provided inside the annular ground line 18 e. The ground line 18 eand the second basic power supply line 15′ are wired at such positionsthat they overlap the ground line 18 and the first basic power supplyline 15, respectively, in the second wiring layer 12. A signal line 16 eand a ground pattern 18 c are provided inside the second basic powersupply line 15′. The signal line 16 e connects between the electronicpart 17 a in the first wiring layer 11 and the electronic part 17 bdescribed below in the fourth layer 14 via through holes, notillustrated. A power supply line 15 a′, which connects between thesecond basic power supply line 15′ and the electronic part 17 b′ in thefirst wiring layer 11 via through holes, not illustrated, is providedinside the second basic power supply line 15′. In the third wiring layer13, the ground pattern 18 c is formed over a region other than the powersupply line and the signal lines such that the minimum requiredclearances in terms of manufacture are provided between the groundpattern 18 c and the power supply lines and the signal lines.

As shown in FIG. 15D, the electronic parts 17 b, 17 c driven at thefirst voltage are mounted on the fourth wiring layer 14. Signal lines 16f, 16 g, 16 h, 16 i, power supply lines 15 b′, 15 e, and a groundpattern 18 d are also provided in the fourth wiring layer 14. The signalline 16 f connects between the electronic part 17 c and the electronicpart 17 b′ in the first wiring layer 11 via through holes, notillustrated. The signal line 16 g connects between the electronic part17 a′ and the electronic part 17 a in the first wiring layer 11 viathrough holes, not illustrated. The signal line 16 h connects betweenthe electronic part 17 b in the fourth wiring layer 14 and theelectronic part 17 b′ in the first wiring layer 11 via through holes,not illustrated. The signal line 16 i connects between the electronicpart 7 c in the fourth wiring layer 14 and the electronic part 17 a inthe first wiring layer 11 via through holes, not illustrated. The powersupply line 15 b′ connects between the second basic power supply line15′ in the third wiring layer 13 and the electronic part 17 a′ in thefirst wiring layer 11 via through holes, not illustrated. The powersupply line 15 e′ connects between the first basic power supply line 15in the second wiring layer 12 and the electronic part 17 c in the fourthwiring layer 14 via through holes, not illustrated. In the fourth wiringlayer 4, the ground pattern 18 d is formed over a region other than thepower supply lines and the signal lines such that the minimum requiredclearances in terms of manufacture are provided between the groundpattern 18 d and the power supply lines and the signal lines.

It should be noted that the ground lines 18, 18 e and ground patterns 18a to 18 d in the respective wiring layers are connected together viathrough holes, not illustrated. Thus, the ground line 18 in the secondwiring layer 12 is designed to have at least a width that allowsformation of through holes. Likewise, the first basic power supply lines15, 15′ are designed to have a width that allows formation of throughholes.

All of the signal lines 16 a to 16 i in the respective wiring layers areprovided inside the first basic power supply line 15 in the secondwiring layer 12 and the second basic power supply line 15′ in the thirdwiring layer 13. The power supply lines 15 a, 15 b, 15 c, 15 d, 15 e, 15a′, 15 b′ and the signal lines 26 a to 26 h in the respective wiringlayers are wired at such positions that they do not overlap each otherwhen they are projected on the same projection plane from above. Thisreduces the effect of cross talk caused by adjacent lines to the leastpossible level.

According to the second embodiment, the multi-layered printed wiringboard has the second wiring layer 12 in which the ground line 18 isformed at the outer edge thereof and the basic power supply line 15 isformed adjacent to and inside the ground line 18, and the third wiringlayer 13 in which the ground line 18 e is provided at the outer edge andthe second basic power supply line 15′ is formed adjacent to and insidethe ground line 18 e. The power supply lines 15 a, 15 b, 15 c, 15 d, 15e connected to the first basic power supply line 15 supply power to theelectronic parts 17 a, 17 b, 17 c driven at the first voltage viapredetermined wiring layers. The power supply lines 15 a′, 15 b′connected to the second basic power supply line 15′ supply power to theelectronic parts 17 a′, 17 b′ driven at the second voltage viapredetermined wiring layers.

As described above, the multi-layered printed wiring board according tothe second embodiment is capable of satisfactorily reducing radiationnoises without lowering the wiring density when power of differentvoltages is supplied to the multi-layered printed board, because thesecond power supply line 15′ is provided at a position where the firstpower supply line 15 is projected when they are projected on the sameprojection plane.

(Third Embodiment)

FIGS. 6A-6D are schematic diagrams showing the construction of amulti-layered printed wiring board according to a third embodiment ofthe present invention. FIG. 7 is a schematic diagram showing theconstruction of all layers of the multi-layered printed wiring boardaccording to the third embodiment when they are fluoroscopically viewedfrom above, and is intended to provide a supplemental description of theconnection and positional relationship between signal lines.

The multi-layered printed wiring board according to the third embodimentsupplies power to electronic parts 27 a, 27 b, 27 c driven at a firstvoltage, and electronic parts 27 a′, 27 b′ driven at a second voltagedifferent from the first voltage.

The multi-layered printed wiring board according to the secondembodiment is comprised of a first wiring layer 21, a second wiringlayer 22, a third wiring layer 23, and a fourth wiring layer 24. Theelectronic parts driven at two different voltages are mounted on thefirst wiring layer 21 and the fourth wiring layer 24.

As shown in FIG. 6A, the electronic parts 27 a, 27 b, 27 c driven at thefirst voltage and the electronic part 27 a′ driven at the second voltageare mounted on the first wiring layer 21, and signal lines 26 a, 26 band a ground pattern 28 a are provided in the first wiring layer 21. Thesignal line 26 a connects between the electronic part 27 a in the firstwiring layer 21 and the electronic part 27 b′ in the fourth layer 24,appearing in FIG. 6D, via through holes, not illustrated. The signalline 26 b connects between the electronic part 27 a′ and the electronicpart 27 b. The power supply line 25 a connects between the first basicpower supply line 25 in the second wiring layer 22, appearing in FIG.6B, and the electronic part 27 c in the fourth wiring layer 24,appearing in FIG. 6D, via through holes, not illustrated. In the firstwiring layer 21, the ground pattern 28 a is over a region other than thepower supply line and the signal lines such that the minimum requiredclearances in terms of manufacture are provided between the groundpattern 28 a and the power supply line and the signal lines.

As shown in FIG. 6B, an annular ground line 28 is provided in the secondwiring layer 22, the first annular basic power supply line 25 isprovided inside the ground line 28, second basic power supply line 25′is provided inside the basic power supply line 25, and signal lines 26c, 26 d are provided inside the second basic power supply line 25′. Thesignal line 26 c connects between the electronic part 27 a and theelectronic part 27 a′ in the first wiring layer 21 via through holes,not illustrated. The signal line 26 d connects between the electronicpart 27 b in the first wiring layer 21 and the electronic part 2 c inthe fourth wiring layer 24 via through holes, not illustrated. Insidethe second basic power supply line 25′ in the second wiring layer 22,the ground pattern 28 b is formed over a region other than the powersupply lines and the signal lines such that the minimum requiredclearances in terms of manufacture are provided between the groundpattern 28 b and the power supply lines and the signal lines.

As shown in FIG. 6C, a signal line 26 e, power supply lines 25 b, 25 a′,25 b′, and a ground pattern 28 c are provided in the third wiring layer23. The signal line 26 e connects between the electronic part 27 b inthe first wiring layer 21 and the electronic part 27 b′ in the fourthwiring layer 24 via through holes, not illustrated. The power supplyline 25 b connects between the first basic power supply line 25 in thesecond wiring layer 22 and the electronic part 27 a in the first wiringlayer 11 via through holes, not illustrated. The power supply line 25 a′connects between the second basic power supply line 25′ in the secondwiring layer 22 and the electronic part 27 a′ in the first wiring layer21 via through holes, not illustrated. The power supply line 25 b′connects between the second power supply line 25′ in the second wiringlayer 22 and the electronic part 27 b in the fourth wiring layer 24 viathrough holes, not illustrated. In the third wiring layer 23, the groundpattern 28 c is formed over a region other than the power supply linesand the signal lines such that the minimum required clearances in termsof manufacture are provided between the ground pattern 28 c and thepower supply lines and the signal lines.

As shown in FIG. 6D, the electronic parts 27 c driven at the firstvoltage and the electronic parts 27 b′ driven at the second voltage aremounted on the fourth wiring layer 24. Signal lines 26 f, 26 g, 26 h, apower supply line 25 c, and a ground pattern 28 d are provided in thefourth wiring layer 24. The signal line 26 f connects between theelectronic part 27 c and the electronic part 27 a in the first wiringlayer 21 via through holes, not illustrated. The signal line 26 gconnects between the electronic part 27 c in the fourth wiring layer 24and the electronic part 27 a′ in the first wiring layer 21 via throughholes, not illustrated. The signal line 26 h connects between theelectronic part 27 b′ in the fourth wiring layer 24 and the electronicpart 27 a′ in the first wiring layer 21 via through holes, notillustrated. The power supply line 25 c connects between the first basicpower supply line 25 in the second wiring layer 22 and the electronicpart 27 b in the first wiring layer 21 via through holes, notillustrated. In the fourth wiring layer 24, the ground pattern 28 d isformed over a region other than the power supply line and the signallines such that the minimum required clearances in terms of manufactureare provided between the ground pattern 28 d and the power supply lineand the signal lines.

It should be noted that the ground line 28 and ground patterns 28 a to28 d in the respective wiring layers are connected together via throughholes, not illustrated. Thus, the ground line 28 in the second wiringlayer 22 is designed to have at least a width that allows formation ofthrough holes. Likewise, the first and second basic power supply lines25, 25′ are designed to have a width that allows formation of throughholes.

As shown in FIG. 7, all of the signal lines 26 a to 26 h in therespective wiring layers are provided inside the second basic powersupply line 25′ in the second wiring layer 22. The power supply lines 25a, 25 b, 25 c, 25 a′, 25 b′ and the signal lines 26 a to 26 h in therespective wiring layers are wired at such positions that they do notoverlap each other when they are projected on the same projection planefrom above. This reduces the effect of cross talk caused by adjacentlines to the least possible level. The ground patterns 28 a to 28 d areomitted from FIG. 7 in order to make the drawing more understandable.

According to the third embodiment, the second basic power supply line25′ is provided adjacent to and inside the first basic power supply line25 wired at the outer edge of the second wiring layer 22. The powersupply lines 25 a, 25 b, 25 c connected to the first basic power supplyline 25 supply power to the electronic parts 27 a, 27 b, 27 c driven atthe first voltage via predetermined layers. The power supply lines 25a′, 25 b′ connected to the second basic power supply line 25′ supplypower to the electronic parts 27 a′, 27 b′ driven at the second voltagevia predetermined layers.

As described above, the multi-layered printed wiring board according tothe third embodiment is capable of achieving the same effects as thefirst embodiment and also satisfactorily reducing radiation noiseswithout lowering the wiring density when power of different voltages issupplied to the multi-layered printed board, because the second powersupply line 25′ is provided inside the first power supply line 25.

(Fourth Embodiment)

FIGS. 8A-8D are schematic diagrams showing the construction of amulti-layered printed wiring board according to a fourth embodiment ofthe present invention. Signal lines, electronic parts, power supplylines, ground lines inside basic power supply lines are omitted fromthese figures and a description thereof is also omitted herein. FIG. 9is a schematic sectional view showing a section of the multi-layeredprinted wiring board according to the fourth embodiment, and is intendedto provide a supplementary description of the positional relationshipbetween the ground line at the outer edge and the basic power supplyline in the respective wiring layers.

In the multi-layered printed wiring board according to the fourthembodiment, power supply lines that supply different voltages areprovided at the outer edge of each of wiring layers (four wiring layersin the fourth embodiment).

The multi-layered printed wiring board according to the fourthembodiment is comprised of a first wiring layer 31, a second wiringlayer 32, a third wiring layer 33, and a fourth wiring layer 34.

As shown in FIGS. 8A and 9, a ground line 38 a is provided at the outeredge of the first wiring layer 31, and a first basic power supply line35 a is provided inside the ground line 38 a. A signal line 36 a isprovided inside the first basic power supply line 35 a.

As shown in FIGS. 8B and 9, a ground line 38 b, which is connected tothe ground line 38 a in the first wiring layer 31 via through holes 39a, is provided at the outer edge of the second wiring layer 32, and asecond basic power supply line 35 b is provided inside the ground line38 b. A ground pattern 38 e and a signal line 36 b are provided insidethe second basic power supply line 35 b. The ground line 38 b and thesecond basic power supply line 35 b are wired at positions where theground line 38 a and the first basic power supply line 35 a areprojected when they are projected on the same projection plane.

As shown in FIGS. 8C and 9, a ground line 38 c, which is connected tothe ground line 38 b in the second wiring layer 32 via the through holes39 a, is provided at the outer edge of the third wiring layer 33, and athird basic power supply line 35 c is provided inside the ground line 38c. A signal line 36 c and a ground pattern 38 f are provided inside thethird basic power supply line 35 c. The ground line 38 c is wider thanthe ground lines 38 a, 38 b, 38 d in the other wiring layers. Althoughthe position of the outside of the ground line 38 c corresponds to thepositions of the outsides of the ground lines in the other wiringlayers, the position of the inside of the ground line 38 c is locatedinside the ground lines in the other wiring layers and connected to theground pattern 38 e in the second wiring layer via through holes 39 b.The ground pattern 38 f is connected to the ground pattern 38 e in thesecond wiring layer 32 via through holes 39 c.

As shown in FIGS. 8D and 9, a ground line 38 d, which is connected tothe ground line 38 c in the third wiring layer 33 via the through holes39 a, is provided at the outer edge of the fourth wiring layer 34, and afourth basic power supply line 35 d is provided inside the ground line38 d. A signal line 36 d is provided inside the fourth basic powersupply line 35 d. The ground line 38 d and the fourth basic power supplyline 35 d are wired at positions where the ground line 38 a and thefirst basic power supply line 35 a in the first wiring layer 31 areprojected when all of them are projected on the same projection plane.

It should be noted that all of the first to fourth basic power supplylines may supply different voltages, or two or three ones of the firstto fourth basic power supply lines may supply the same voltage.

As described above, the multi-layered printed wiring board according tothe fourth embodiment is capable of achieving the same effects as thefirst embodiment and also satisfactorily reducing radiation noiseswithout lowering the wiring density when power of different voltages issupplied to all the wiring layers of the multi-layered printed board,because the basic power supply line in at least one wiring layer (in thefourth embodiment, the basic power supply line 35 c in the third wiringlayer) is provided inside the basic power supply lines in the otherwiring layers, and the widened ground line is provided outside the basicpower supply line and connected to the inner ground line.

(Other Embodiments)

1) Although the above described first to fourth embodiments are eachimplemented as a single multi-layered printed wiring board, there is nointention to limit the invention to this, but the present invention maybe applied to a single apparatus (e.g. copying machines, functioncombined copying machines, various kinds of printers, scanners,facsimile machines, digital cameras, and the like) in which is installedthe multi-layered printed wiring board according to the presentinvention.

2) Although the above described first to fourth embodiments are eachimplemented as a single multi-layered printed wiring board, there is nointention to limit the invention to this, but the present invention maybe applied to a system (e.g. an image formation system, an image readingsystem, an image communication system, and an imaging system) that iscomprised of a plurality of electronic apparatuses (e.g. copyingmachines, function combined copying machines, various kinds of printers,scanners, facsimiles, digital cameras, and the like) in which isinstalled the multi-layered printed wiring board according to thepresent invention.

What is claimed is:
 1. A multi-layered printed wiring board having atleast three wiring layers, said wiring layers each having an outer edge,comprising: a ground line formed at the outer edge of at least one ofsaid wiring layers; a ground pattern; a basic power supply line formedinside said ground line on the at least one of said wiring layers onwhich said ground line is formed; at least one power supply lineextending from said basic power supply line; a plurality of electronicparts mounted on at least one of said wiring layers; a signal line; eachof said wiring layers having at least two selected from the groupconsisting of said ground line or said ground pattern, said basic powersupply line or said at least one power supply line, and said signalline; and wherein said at least one power supply line is wired tomounting positions of said electronic parts via at least one of saidwiring layers, and said power supply line is formed inside said basicpower supply line when said power supply line and said basic powersupply line are projected on one projection plane.
 2. A multi-layeredprinted wiring board according to claim 1, wherein said ground line andsaid basic power supply line are each shaped substantially in a form ofan annulus and arranged adjacent to each other.
 3. A multi-layeredprinted wiring board according to claim 2, comprising: a signal lineprovided in each of said wiring layers, said signal line connectingbetween ones of said electrical parts mounted on one of said wiringlayers or connecting between ones of said electrical parts mounted onrespective different ones of said wiring layers via at least one of saidwiring layers; and wherein said power supply line and said signal lineare formed inside said basic power supply line when said power supplyline, said signal line, and basic power line are projected on oneprojection plane.
 4. A multi-layered printed wiring board having atleast three wiring layers each at leant having at least three wiringlayers, said wiring layers each having an outer edge, comprising: aground line formed at the outer edge of at least one of said wiringlayers; a plurality of electronic parts mounted on at least one of saidwiring layers; at least one power supply line provided in apredetermined one of said wiring layers at a location inside said groundline on the at least one of said wiring layers on which said ground lineis formed, said at least one power supply line being wired to mountingpositions of said electronic parts via at least one other one of saidwiring layers; a signal line provided in each of said wiring layers,said signal line connecting between ones of said electrical partsmounted on one of said wiring layers or connecting between ones of saidelectrical parts mounted on respective different ones of said wiringlayers via at least one of said wiring layers; and a ground patternformed over a region other than said power supply line and said signalline and connected to said ground line, each of said wiring layershaving at least two selected from the group consisting of said aroundline or said ground pattern, said basic power supply line or said atleast one power supply line, and said signal line.
 5. A multi-layeredprinted wiring board according to claim 4, wherein said ground line andsaid ground pattern are formed such that said ground line and saidground pattern substantially entirely cover said multi-layered printedwiring board when said ground line and said ground pattern are projectedon one projection plane.
 6. A multi-layered printed wiring boardaccording to claim 4, comprising: a basic power supply line formed atthe outer edge of at least one of said wiring layers at a locationadjacent to and inside said ground line; wherein said power supply lineis formed inside said basic power supply line on the at least one ofsaid wiring layers on which said basic power supply line is formed andextends from said basic power supply line via at least one of saidwiring layers such that said power supply line is wired to mountingpositions of said electrical parts; and wherein said signal line isformed inside said basic power supply line, said signal line connectingbetween ones of said electrical parts mounted on one of said wiringlayers or connecting between ones of said electrical parts mounted onrespective different ones of said wiring layers via at least one of saidwiring layers.
 7. A multi-layered printed wiring board according toclaim 6, wherein said ground line and said basic power supply line areeach shaped substantially in a form of an annulus and arranged adjacentto each other.
 8. A multi-layered printed wiring board according toclaim 4, wherein said power supply line and said signal line arearranged so as not to overlap said power supply line and said signalline in at least one other one of said wiring layers which is adjacentto said at least one of said wiring layers on which said power supplyline is formed, when said power supply line and said signal line areprojected on one projection plane.
 9. A multi-layered printed wiringboard having at least three wiring layers, said multi-layered printedwiring board comprising: a first wiring layer constituting one of saidwiring layers, and having a ground line formed at the outer edge of saidfirst wiring layer, a first basic power supply line formed adjacent toand inside said ground line, and a first power supply line extendingfrom said first basic power supply line; a second wiring layerconstituting one of said wiring layers, and having a ground patternformed at the outer edge of said second wiring layer, a second basicpower supply line for supplying a different voltage from a voltagesupplied by said first basic power supply line, said second basic powersupply line being formed at a position where said first basic powersupply line is projected when said second basic power supply line andsaid first basic power supply line are projected on one projectionplane, and a second power supply line extending from said second basicpower supply line; and a plurality of electronic parts mounted on atleast one of said wiring layers; a signal line; each of said wiringlayers having said signal line, and at least two selected from the groupconsisting of said ground line or said ground pattern, said first basicpower supply line, said second power supply line, said first powersupply line, and said second basic power supply line; wherein said firstand second power supply lines extending from said first and second basicpower supply lines, respectively are wired to mounting positions of saidelectronic parts via at least one of said wiring layers.
 10. Amulti-layered printed wiring board according to claim 9, wherein saidground line, said ground pattern, and said first and second basic powersupply lines are each shaped substantially in a form of an annulus. 11.A multi-layered printed wiring board according to claim 10, comprising:a signal line provided in each said wiring layers, said signal lineconnecting between ones of said electrical parts mounted on one of saidwiring layers or connecting between ones of said electrical partsmounted on respective different ones of said wiring layers via at leastone of said wiring layers; and a ground pattern formed over a regionother than said first and second power supply lines and said signal lineand connected to said ground line and said ground pattern; and whereinsaid first and second power supply lines and said signal line are formedinside said first and second basic power supply lines.
 12. Amulti-layered printed wiring board having at least three wiring layers,said wiring layers each having an outer edge, comprising: a ground lineformed at the outer edge of at least one of said wiring layers; a groundpattern; a first basic power supply line formed adjacent to and insidesaid ground line; a second basic power supply line formed adjacent toand inside said ground line to supply a different voltage from a voltagesupplied by said first basic power supply line; at least two powersupply lines extending from respective ones of said first and secondbasic power supply lines; a plurality of electronic parts mounted on atleast one of said wiring layers; and a signal line: each of said wiringlayers having at least two selected from the group consisting of saidground line or said around pattern, said first basic power supply line,said second basic power supply line, said at least two power supplylines, and said signal line: wherein said power supply lines are wiredto mounting positions of said electronic parts via at least one of saidwiring layers.
 13. A multi-layered printed wiring board according toclaim 12, wherein said ground line and said first and second basic powersupply lines are shaped substantially in a form of an annulus.
 14. Amulti-layered printed wiring board according to claim 12, comprising: asignal line provided in each of said wiring layers, said signal lineconnecting between ones of said electrical parts mounted on one of saidwiring layers or connecting between ones of said electrical partsmounted on respective different ones of said wiring layers via at leastone of said wiring layers; and a ground pattern formed over a regionother than said power supply lines and said signal line and connected tosaid ground line; wherein said power supply lines and said signal lineare formed inside said second basic power supply line.
 15. Amulti-layered printed wiring board having at least three wiring layers,said wiring layers each having an outer edge, comprising: a ground lineformed at the outer edge of each of said wiring layers; a basic powersupply line formed adjacent to and inside said ground line in each ofsaid wiring layers; a plurality of electronic parts mounted on at leastone of said wiring layers; at least one power supply line provided in atleast one of said wiring layers at a location inside said basic powersupply line, said at least one power supply line extending from saidbasic power supply line via at least one other one of said wiring layersand wired to mounting positions of said electronic parts; a signal lineprovided in each of said wiring layers, said signal line connectingbetween ones of said electrical parts mounted on one of said wiringlayers or connecting between ones of said electrical parts mounted onrespective different ones of said wiring layers via at least one of saidwiring layers; and a ground pattern formed over a region other than saidpower supply line and said signal line at a location inside said basicpower supply line in at least one of said wiring layers; each of saidwiring layers having at least two selected from the group consisting ofsaid ground line or said ground pattern, said basic power supply line orsaid at least one power supply line, and said signal line: wherein saidground line in at least one of said wiring layers has a width greaterthan said ground line in the other wiring layers and connected to saidground pattern via at least one through hole.